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Advertised vs.
Actual
“8 Watts” Are Not Always 8 Watts
Heraeus Noblelight GmbH
E
ven if “8 Watts” is on the label, eight watts
are not always delivered. Uniform terms,
appropriate measuring equipment and
methods provide information about what
UV source might be suitable for the specific curing
process. Users should consider this when comparing
the output of UV LED systems.
Information about UV LED systems provided in
technical documents is so differing, varied and
often imprecise that it is necessary to take a closer
look. Specification of the measuring equipment
and methods used and knowledge of what variables
are specifically measured are important to enable a
comparison of LEDs and their performance.
UV LED systems can be compared with each other
based on electrical power input and radiant power
output and the efficiency calculated from them.
However, what is useful for an optimal industrial
process, such as the UV curing of coatings, inks,
paints and glues, is information and comparison
values about the intensity, homogeneity and distribu-
tion of the UV radiation.
MEAN POWER DENSITY
Usually, peak values at the exit window are specified. However, these
values are misleading and unsuitable to obtain information about ra-
diation effectiveness. A device with high peak values may have a very
inhomogeneous radiation distribution, resulting in uneven curing.
Moreover, peak values depend on the choice of measuring instru-
ment. For example, measuring results for short distances (less than
0.98 -in./25-mm.) are very much determined by detector properties
and hardly comparable at all.
NOVEMBER 2014 | FLEXO 43
TECHNOLOGY & TECHNIQUES
Figure 1: For the devices measured, the
radiated power in proportion to the window size
varies between 4.0 -W/cm2 and 6.9 -W/cm2
(Photos copyright Heraeus Noblelight GmbH)
Figure 2: Illustration of the benefit of
micro optics on forward irradiance